| 摘要: | 目前空氣品質模式需要將環境部所發布的TEDS排放量清單提供的之道排放量根據其月、日、小時特性進行時序分配，提供污染物排放的情境，目前的方法並未考量到月特性中包含了連續假期遭成的錯估，以及針對連續假期變動明顯的國道交通量並沒有提供對應變化的排放量。
本研究利用TDCS國道電子收費系統提供的高解析度車流量資訊，將對應車種、縣市別的車流量資訊進行計算，在進行權重計算前，優先去除了連續假期日的影響，先製作一分無連續假期的排放量情境，並對各種類型的連假特性提供日排放量倍率，可以彈性的對於假期排放量進行調整。
修正時序分配後的排放量，NOX在春節連續假期間平均每小時減少約0.13噸的排放量而NMHC在竹苗以南的地區增加約0.03噸，而在二月非連續假期的期間，NOX則會每小時增加約0.04噸的排放量，而NMHC則會減少約0.03噸，其排放量情境的改變也符合更加真實車流量，例如假期大貨車的減量導致NOX排放減少，而小客車出遊導致NMHC增加，證明該時序分配法能更好的詮釋模式中真實國道排放的情形。
在更新國道時序分配方法後，對於空氣模式的影響包含直接生成物NOX和NMHC的影響以及二次生成物O3和PM2.5的改變，主要濃度改變在國道周遭的西半部地區，在連續假期間NOX的減少最為顯著，在連續假期之弱綜觀天氣下，早上八點減少可達12~30ppb，且由於國道的西部地區屬於VOC-limited，導致O3的濃度會上升，日間濃度可增加約2~4ppb左右，夜間上升約1~3ppb，同時減少的NOX會使得空氣中的OH自由基增加並與NMHC反應導致NMHC的濃度減少約0.8~1.2ppb，而PM2.5受到氮氧化物二次生成的硝酸鹽類及直接排放的元素碳減少，日間模擬濃度減少每立方公尺0.8~1.2微克及夜間模擬濃度減少每立方公尺0.8~2微克。
與空氣品質監測站比較過後可得知，更改國道排放量時序分配，連假期間可以改善NOx的高估情形，普遍可減少1~2ppb的高估以及減少1~2的RMSE，O3濃度改善原本低估約1~2ppb左右， 且NMHC、PM2.5的RMSE也有些許減少。;The current air quality model requires temporal distribution of the emissions inventory provided by the Taiwan Emission Data System (TEDS), released by the Ministry of Environment, according to their monthly, daily, and hourly characteristics to provide pollution emission scenarios. The current method does not account for the misestimation caused by consecutive holidays in the monthly characteristics and does not provide corresponding emissions changes for significantly variable highway traffic during consecutive holidays.
This study utilizes high-resolution traffic volume data provided by the Traffic Data Collection System (TDCS) for national highways, calculates the traffic volume information corresponding to vehicle types and counties, and prioritizes the removal of the impact of consecutive holiday days before performing the weighting calculations. First, an emission scenario without consecutive holidays is created, and daily emission multipliers for various types of consecutive holiday characteristics are provided, allowing flexible adjustment of holiday emissions.
After correcting the temporal distribution of emissions, NOx emissions during the consecutive Chinese New Year holidays decrease by approximately 0.13 tons per hour on average, while NMHC emissions increase by about 0.03 tons in the areas south of Hsinchu and Miaoli. During February on non-consecutive holidays, NOx emissions increase by approximately 0.04 tons per hour, and NMHC emissions decrease by about 0.03 tons. These changes in the emission scenario align with the actual traffic volume, such as the reduction of NOx emissions due to fewer heavy trucks during holidays and the increase in NMHC due to more private car trips, proving that this temporal distribution method can better interpret the actual highway emissions in the model.
After updating the highway temporal distribution method, the impact on the air quality model includes changes in primary pollutants NOX and NMHC as well as secondary pollutants O3 and PM2.5. The main concentration changes occur in the western part of the region around highways. During consecutive holidays, NOx reductions are most significant, with decreases reaching 12-30 ppb at 8 A.M. under weak synoptic weather conditions. Since the western region along the highways is VOC-limited, O3 concentrations increase, with daytime concentrations rising by about 2-4 ppb and nighttime by about 1-3 ppb. The reduction in NOx also increases the OH radical concentration in the air, reacting with NMHC and resulting in a decrease in NMHC concentration by about 0.8-1.2 ppb. PM2.5 concentrations decrease due to reduced secondary nitrate formation from NOx and direct emissions of elemental carbon, with daytime simulated concentrations decreasing by 0.8-1.2 μg/m³ and nighttime by 0.8-2 μg/m³.
Comparison with air quality monitoring stations indicates that adjusting the highway emission temporal distribution can improve the overestimation of NOx during holidays, generally reducing overestimation by 1-2 ppb and decreasing RMSE by 1-2. The O3 concentration improves from an initial underestimation by about 1-2 ppb, and RMSE for NMHC and PM2.5 also shows some reduction. |
